CAIRO, April 4 (Reuters) - Egyptian authorities deported a rights campaigner hours after he flew in to deliver a petition against death sentences imposed on 529 supporters of deposed president Mohamed Mursi, the man and security officials said on Friday.

Wissam Tarif, a Lebanese citizen from international group Avaaz, was hoping to hand over the appeal at a meeting with the grand mufti, Egypt's top religious authority who reviews all death sentences.

Last month's mass sentencing of the 529 members of Mursi's Muslim Brotherhood in the southern province of Minya was widely criticised by rights organisations and Western governments.

Most of the men were found guilty of murder, carrying out attacks and other offences during clashes after the forced dispersal of two Muslim Brotherhood protest camps in Cairo on Aug. 14.

Turmoil has deepened since the army overthrew Mursi, Egypt's first freely elected president, in July following mass protests against his rule. Security forces have killed hundreds of Brotherhood members in the streets and arrested thousands.

Tarif said he flew into Cairo from Beirut on Tuesday with a Lebanese Muslim cleric.

"I landed at Cairo airport and I wasn't allowed in. My name popped up on the computer and they took me to the deportation room where I was interrogated by political security about the meeting, about the petition, about the mufti," he added.

Tarif said he was barred from leaving the airport to attend the meeting and authorities briefly seized his computer.

Security officials at Cairo airport saod Tarif arrived on Tuesday afternoon and was deported 11 hours later after his name appeared on a watch list.

New York-based Avaaz says it uses the Internet to drum up support for environmental, human rights and other campaigns.

According to its website, more than 1.1 million people have signed its petition "Egypt: Stop the Mass Execution" which describes the proceedings as "a political show trial". (Writing by Tom Perry; Editing by Andrew Heavens)